1. Field of the Invention
This disclosure relates generally to systems, methods, and devices useful for monitoring water to be used, for example, in hydrocarbon production. More specifically, the disclosure relates to an on-line unit for measuring and optimizing the quality of water being used during hydrocarbon recovery or production processes, such as a hydraulic fracturing process.
2. Description of the Related Art
Oil and natural gas from shale formations play important roles in meeting the energy demands of the United States. Development of tight oil in the past few years has allowed domestic production of crude oil to increase from 5.1 million barrels a day in 2007 to 5.5 million barrels a day in 2010, reversing a decline in production that began in 1986. Continued development of tight oil will enable the US to produce 6.7 million barrels a day by 2020. Shale gas production is expected to increase from 5 trillion cubic feet in 2010 (23% of total US gas production) to 13.6 trillion cubic feet in 2035 (49% of total US gas production). To enable this large growth in oil and gas supply, numerous new wells will need to be drilled and stimulated via hydraulic fracturing.
Hydraulic fracturing involves pumping a water-sand-chemical mixture into a well at high pressure to fracture the shale formation surrounding the well and allow the natural gas to flow to the wellbore. The water quantities needed for well stimulation can range from 2 to 5 million gallons per well.
When a well begins producing, some of the water used during the stimulation begins to return to the surface. The first three months of production is called the flowback time, and is when the most water is returned to the surface with the oil and gas. After the flowback period, the flow of water returning to the surface slows, but continues. Over the life of the well, the amount of water that returns to the surface can range from as little as 10% to over 70% of the water used for the stimulation, or between 200,000 to 3.5 million gallons of water.
With such large amounts of water needed during the well stimulation, sourcing can be problematic. Well completion companies will source water wherever it is available. Sources can include livestock ponds, flowback water, produced water, river water, lake water, municipal water, etc. With all of the different sources of water being used in the well stimulation, chemical addition during the hydraulic fracturing process can be troublesome. Various chemicals such as biocides, scale inhibitors, and friction reducers can have dosages dependent upon the water quality, and in some cases, entirely different chemicals may be needed based on what type(s) of water is being used. On the fly changes of water have been known to lead to chemical over-dosage that deleteriously affects the fracturing process. An online tool for monitoring water quality during a fracturing process that would allow for proper chemical dosage would prohibit these harmful side effects.